Stack of horizontally extending and vertically overlapping features, methods of forming circuitry components, and methods of forming an array of memory cells

ABSTRACT

A method of forming circuitry components includes forming a stack of horizontally extending and vertically overlapping features. The stack has a primary portion and an end portion. At least some of the features extend farther in the horizontal direction in the end portion moving deeper into the stack in the end portion. Operative structures are formed vertically through the features in the primary portion and dummy structures are formed vertically through the features in the end portion. Horizontally elongated openings are formed through the features to form horizontally elongated and vertically overlapping lines from material of the features. The lines individually extend from the primary portion into the end portion, and individually laterally about sides of vertically extending portions of both the operative structures and the dummy structures. Sacrificial material that is elevationally between the lines is at least partially removed in the primary and end portions laterally between the horizontally elongated openings. Other aspects and implementations are disclosed.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 13/085,083, filed Apr. 12, 2011, entitled “Stack OfHorizontally Extending And Vertically Overlapping Features, Methods OfForming Circuitry Components, And Methods Of Forming An Array Of MemoryCells”, naming Sanh D. Tang, Roger W. Lindsay, and Krishna K. Parat asinventors, the disclosure of which is incorporated by reference.

TECHNICAL FIELD

Embodiments disclosed herein pertain to stacks of horizontally extendingand vertically overlapping features, and to methods of forming circuitrycomponents and to methods of forming an array of memory cells.

BACKGROUND

Integrated circuits are often formed on a semiconductor substrate suchas a silicon wafer or other semiconductive material. In general, layersof various materials which are semiconductive, conductive, orelectrically insulative are utilized to form the integrated circuits. Byway of examples, the various materials may be doped, ion implanted,deposited, etched, grown, etc. using various processes. A continuinggoal in semiconductive processing is to strive to reduce the size ofindividual circuitry components, thereby enabling smaller and denserintegrated circuitry.

Memory is one type of integrated circuitry, and is used in computersystems for storing data. Such is usually fabricated in one or morearrays of individual memory cells. The memory cells might be volatile,semi-volatile, or nonvolatile. Nonvolatile memory cells can store datafor extended periods of time, in many instances including when thecomputer is turned off. Volatile memory dissipates and thereforerequires being refreshed/rewritten, in many instances multiple times persecond. Regardless, the smallest unit in each array is termed as amemory cell and is configured to store data as one of at least twodifferent selectable states. In a binary system, the states areconsidered as either a “0” or a “1”. In other systems, at least someindividual memory cells may be configured to store data as one of morethan two selectable states.

Integrated circuitry fabrication continues to strive to produce smallerand denser integrated circuits. Accordingly, the fewer components anindividual circuit device has, the smaller the construction of thefinished device can be. A simple memory cell will be comprised of twoconductive electrodes having a programmable material there-between. Theprogrammable material is selected or designed to be configured in aselected one of at least two different physical memory states to enablestoring of information by an individual memory cell. The reading of thecell comprises determination of which of the states the programmablematerial is in, and the writing of information to the cell comprisesplacing the programmable material in a target memory state. Someprogrammable materials retain a memory state in the absence of refresh,and thus may be incorporated into nonvolatile memory cells.

Some programmable materials may contain mobile charge carriers largerthan electrons and holes, for example ions in some example applications.Regardless, the programmable materials may be converted from one memorystate to another by moving the mobile charge carriers to alter adistribution of charge density within the programmable materials. Someexample memory devices that utilize ions as mobile charge carriers areresistive RAM (RRAM) cells, which can include classes of memory cellscontaining multivalent oxides, and which can include memristors in somespecific applications. Other example memory devices that utilize ions ascharge carriers are programmable metallization cells (PMCs); which maybe alternatively referred to as a conductive bridging RAM (CBRAM),nanobridge memory, or electrolyte memory.

The RRAM cells may contain programmable material sandwiched between apair of electrodes. The programming of the RRAM cells may comprisetransitioning the programmable material between first a memory state inwhich charge density is relatively uniformly dispersed throughout thematerial and a second memory state in which the charge density isconcentrated in a specific region of the material (for instance, aregion closer to one electrode than the other).

A PMC may similarly have programmable material sandwiched between a pairof current conductive electrodes. The PMC programmable materialcomprises ion conductive material, for example a suitable chalcogenideor any of various suitable oxides. A suitable voltage applied across theelectrodes generates current conductive super-ionic clusters orfilaments. Such result from ion transport through the ion conductivematerial which grows the clusters/filaments from one of the electrodes(the cathode), through the ion conductive material, and toward the otherelectrode (the anode). The clusters or filaments create currentconductive paths between the electrodes. An opposite voltage appliedacross the electrodes essentially reverses the process and thus removesthe current conductive paths. A PMC thus comprises a high resistancestate (corresponding to the state lacking a current conductive filamentor clusters between the electrodes) and a low resistance state(corresponding to the state having a current conductive filament orclusters between the electrodes), with such states being reversiblyinterchangeable with one another.

Another type of nonvolatile memory is known as flash memory, a type ofEEPROM (electrically-erasable programmable read-only memory) that may beerased and reprogrammed in groups. A typical flash memory array includesa large number of nonvolatile memory cells usually grouped into blocks.Each of the cells within a block may be electrically programmed bycharging its programmable gate material. The charge may be removed fromthe programmable gate material by a block erase operation. NAND is abasic architecture of flash memory. A NAND architecture comprises atleast one select gate coupled in series to a serial combination ofmemory cells (with the serial combination being commonly referred to asa NAND string).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic oblique view of a semiconductor substratefragment in process in accordance with an embodiment of the invention.

FIG. 2 is a view of the FIG. 1 substrate at a processing step subsequentto that shown by FIG. 1.

FIG. 3 is a view of the FIG. 2 substrate at a processing step subsequentto that shown by FIG. 2.

FIG. 4 is a view of the FIG. 3 substrate at a processing step subsequentto that shown by FIG. 3.

FIG. 5 is a view of the FIG. 4 substrate at a processing step subsequentto that shown by FIG. 4.

FIG. 6 is an end view of FIG. 5 relative to line 6-6 in FIG. 5.

FIG. 7 is a view of the FIG. 5 substrate wherein certain material inFIG. 5 is not shown in FIG. 7 solely for clarity.

FIG. 8 is an end view of FIG. 7 relative to line 8-8 in FIG. 7.

FIG. 9 is a view of the FIG. 7 substrate at a processing step subsequentto that shown by FIG. 7.

FIG. 10 is a view of the FIG. 9 substrate wherein certain material inFIG. 9 is not shown in FIG. 10 solely for clarity.

FIG. 11 is a view of the FIG. 9 substrate at a processing stepsubsequent to that shown by FIG. 9.

FIG. 11A is an enlarged view of a portion of FIG. 11.

FIG. 12 is view of the FIG. 11 substrate wherein certain material inFIG. 11 is not shown in FIG. 12 solely for clarity.

FIG. 13 is a view of the FIG. 12 substrate at a processing stepsubsequent to that shown by FIG. 12.

FIG. 14 is a diagrammatic perspective view of a semiconductor substratefragment in process in accordance with an embodiment of the invention.

FIG. 15 is a view of the FIG. 14 substrate at a processing stepsubsequent to that shown by FIG. 14.

FIG. 16 is a view of the FIG. 15 substrate at a processing stepsubsequent to that shown by FIG. 15.

FIG. 17 is a view of the FIG. 16 substrate at a processing stepsubsequent to that shown by FIG. 16.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments in accordance with the invention of methods offorming circuitry components are initially described with reference toFIGS. 1-10. In some embodiments, an array of memory cells may befabricated, for example as described with reference to FIGS. 1-13 andwith reference to FIGS. 14-17. In one embodiment, such may comprisecross-point memory cells (e.g., as shown in FIG. 17), and in oneembodiment may comprise NAND circuitry (e.g., as shown in FIGS. 11, 11A,12, and 13).

Referring to FIG. 1, a substrate fragment 10 comprises a suitable basesubstrate 13 over which various materials have been provided. Basesubstrate 13 may be homogenous or non-homogenous, for example comprisingmultiple different composition materials and/or layers. As examples,such may comprise bulk monocrystalline silicon and/or asemiconductor-on-insulator substrate. As an additional example, such maycomprise dielectric material having contacts (e.g., conductive vias)formed therein which extend vertically or otherwise into communicativecontact (e.g., current conductive electrical connection) with devicecomponents, regions, or material that is elevationally inward of thedielectric material. In this document, vertical is a direction generallyorthogonal to a primary surface relative to which the substrate isprocessed during fabrication and which may be considered to define agenerally horizontal direction. Further, “vertical” and “horizontal” asused herein are generally perpendicular directions relative one anotherindependent of orientation of the substrate in three-dimensional space.Further in this document, “elevational” and “elevationally” are withreference to the vertical direction from a base substrate upon which thecircuitry is fabricated.

The base substrate may or may not be a semiconductor substrate. In thecontext of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

In one embodiment, substrate 10 comprises a stack of alternatingsacrificial material 12 and dielectric material 14 formed over basesubstrate 13. Each material 12 and 14 may be homogenous ornon-homogenous. In one embodiment, the respective sacrificial materials12 are of the same composition relative one another. In one embodiment,the respective dielectric materials 14 are of the same compositionrelative one another. Regardless, sacrificial material 12 may beselectively etchable, in one embodiment highly selectively etchable,relative to dielectric material 14. In the context of this document, a“selective” etch requires removal of the stated one material relative toanother at a rate of at least 1.5:1, and a highly selective etch at arate of at least about 10:1. Sacrificial material 12 may be any one ormore of conductive (e.g., current conductive), dielectric, orsemiconductive. By way of an example only, dielectric material 14 maycomprise silicon dioxide (whether doped or un-doped), and an examplesacrificial material is a conductive or insulative nitride, for exampletitanium nitride or silicon nitride, respectively. A dielectric material16 and a hardmask 18 have been provided outwardly of alternatingmaterials 12, 14. Each material 16 and 18 may be homogenous ornon-homogenous. Dielectric material 16 may be of the same composition asdielectric material 14, and hardmask material 18 may be of the samecomposition as sacrificial material 12. FIG. 1 depicts vertical tiers ofthree sacrificial materials 12 with two alternating dielectric materials14. Additional alternating pairs of sacrificial and dielectric materialsmay be provided elevationally inward of innermost sacrificial material12 or elevationally outward of outermost sacrificial material 12.

Stack of alternating materials 12, 14 may be considered as comprising aprimary portion 18 and an end portion 20. The end portion in thedepicted embodiment has been patterned to form a stair step-likeconstruction. Such may be formed to provide horizontal area for laterforming contacts to components, regions, or material in end portion 20as will be apparent in the continuing discussion. In one embodiment andas shown, end portion 20 comprises individual stairs 21 which at leastinclude sacrificial material 12.

In one embodiment, materials 12 and 14 may be features (e.g., plates),such as plates or features that are plate-like, whether continuouslyand/or discontinuously formed. In one embodiment, a method of formingcircuitry components comprises forming a stack of horizontally extendingand vertically overlapping plates at least some of which increase inhorizontal extent in the vertical inward direction in the end portion ofthe stack (i.e., at least some of which extend farther in the horizontaldirection in the end portion moving deeper into the stack in the endportion). Either of collective materials 12 or 14 may be considered insuch example embodiment as comprising such plates, or materials 12 and14 in combination in the depicted embodiment may be considered as suchplates. In one embodiment, the horizontally extending and verticallyoverlapping plates are dielectric, for example plates 14 regardless ofthe composition of sacrificial material 12. In one embodiment, all ofthe plates increase in horizontal extent in the vertical inwarddirection in the end portion of the stack. For example in the embodimentof FIG. 1, either of collective plates 12 or collective plates 14 may beconsidered as plates all of which increase in horizontal extentprogressing vertically inward in the end portion of the stack.Alternately, a composite of each immediately adjacent plate pairs 12, 14may be considered as respective plates which increase in horizontalextent in the vertical inward direction in end portion 20 of the stack.

In one embodiment, primary portion 18 and end portion 20 comprise aportion of an array area 22 within which a plurality of memory cellswill be fabricated. Logic circuitry (not shown) may be fabricatedoutside of the array area. Control and/or other peripheral circuitry(not shown) for operating the memory array may or may not fully orpartially be within the array area, with an example array area as aminimum encompassing all of the memory cells of the givenarray/sub-array. Further, multiple sub-arrays might also be fabricatedand operated independently, in tandem, or otherwise relative oneanother. As used in this document, a “sub-array” may also be consideredas an array.

Referring to FIG. 2, dielectric material has been formed over substrate10 and planarized at least to the outermost surface of hardmask 18. Thedielectric material may be homogenous or non-homogenous and, in oneembodiment, may be of the same composition as that of material 14 and isso shown and designated in the figures.

Referring to FIG. 3, first openings 25 have been formed into primaryportion 18 of the stack and second openings 27 have been formed into endportion 20 of the stack. Any openings which overlap the primary and endportions may be such first or second openings (i.e., as primary portionopenings or end portion openings), with example such openings beingshown in FIG. 3 and designated as second openings 27. Openings 25, 27may be formed through each plate 12, 14. An example technique forforming openings 25, 27 is by photolithographic patterning followed bysubtractive anisotropic etching. First openings 25 need not be of thesame shape and/or density relative one another. Second openings 27 neednot be of the same shape and/or density relative one another, orrelative to any one or more of first openings 25. As examples, openings25 and 27 may be formed to have the same horizontal and vertical crosssections (not shown). Alternately, openings 25 and 27 may be formed tohave at least one of different horizontal cross sections (as shown) ordifferent vertical cross sections (as shown). Further and regardless,openings 25 and 27 may be formed at the same time or at different times,and/or may use the same masking step or different masking steps where,for example, photolithographic or other masking is used. In oneembodiment and as shown, at least some of openings 27 in end portion 20are formed to horizontally overlap ends of individual plates 12 and/or14.

At least one of conductive material, semiconductive material, andprogrammable material is/are deposited into the openings. In oneembodiment where conductive material is deposited into the openings,such may comprise current conductive material. In the context of thisdocument, current conductive material can include a composition whereelectric current flow may inherently occur therein predominantly bymovement of subatomic positive and/or negative charges when such aregenerated as opposed to predominantly by movement of ions. Examplecurrent conductive materials are elemental metals, alloys of elementalmetals, current conductive metal compounds, and conductively dopedsemiconductive material, including any combinations thereof.

In one embodiment, the depositing of the conductive material,semiconductive material and/or programmable material occurssimultaneously into all of the openings in the primary portion. In oneembodiment, the depositing of such material occurs simultaneously intoall of the openings in the end portion. In one embodiment, thedepositing of such material occurs simultaneously into all of theopenings in both of the primary and end portions. Operative structures(e.g., circuit components, such as local vertical extensions) are formedtherewith within the openings in the primary portion, and dummystructures (e.g. dummy vertical extensions) are formed therewith withinthe openings in the end portion. In the context of this document, a“dummy” structure is a structure which is used to mimic a physicalproperty of another structure (e.g., load carrying ability of anoperative structure) and which may comprise a circuit inoperableelectrical dead end (e.g., is not part of a current flow path of acircuit even if conductive). Openings in which dummy structures areformed may be considered as “dummy openings”.

For example referring to FIG. 4, a material 30 has been deposited withinopenings 25, 27, and then planarized back through hardmask material 18(not shown). An example thickness for material 30 is from about 100 toabout 150 Angstroms. Material 30 may be homogenous or non-homogenous,and may comprise one or more of conductive material (e.g., currentconductive material), semiconductive material, and programmablematerial. In one embodiment, material 30 comprises semiconductivematerial. Further in such embodiment, the semiconductive material maycomprise interconnected channels of a plurality of vertically orientedtransistors, and in one embodiment comprises interconnected channels ofvertically oriented charge storage transistors as will be apparent fromthe continuing discussion. Regardless, in one embodiment, material 30may form operative structures 31 (e.g., operative circuit components 31)within primary portion openings 25 and form dummy structures 32 (e.g.,dummy circuit components) within end portion openings 27. In oneembodiment and as shown, such operative structures 31 and dummystructures 32 are in the form of hollow cylinders. Alternately by way ofexample, such may be in the form of laterally solid pillars (not shownin FIG. 4). Regardless, the above processing describes but examples offorming operative structures 31 vertically through plates 12 and/or 14in primary portion 18 and forming dummy structures 32 vertically throughplates 12 and/or 14 in end portion 20. In one embodiment, the operativeand dummy structures may comprise the same material (as shown). In oneembodiment, the operative and dummy structures may comprise a pluralityof the same materials (not shown in FIG. 4), and in one such embodimentbe arranged in the same lateral order relative one another in theoperative and dummy structures. In one embodiment, the operative anddummy structures may consist essentially of the same material.

Referring to FIGS. 5-8, horizontally elongated openings 34 (e.g.,trenches) have been formed through plates 12 and/or 14, and laterallybetween material 30, to form horizontally elongated and verticallyoverlapping lines 36 from material of the plates. Lines 36 individuallyextend from primary portion 18 into end portion 20 and individuallylaterally about sides of vertically extending portions of both operativestructures 31 and dummy structures 32. FIGS. 7 and 8 are views of FIGS.5 and 6, respectively, wherein dielectric material 14 added in FIG. 2 isremoved solely for clarity in such drawings. Where either of operativestructures 31 or dummy structures 32 are upwardly open (e.g., as shown),such may be partially or wholly filled (not shown) with dielectricand/or other material prior to the forming of horizontally elongatedopenings 34.

Referring to FIGS. 9 and 10, at least some of sacrificial material 12that is elevationally between lines 36 within primary portion 18 and endportion 20 has been removed from being laterally between horizontallyelongated openings 34. Such thereby, in one embodiment, forms voidspaces 29 elevationally between vertically spaced horizontal dielectriclines 36. An example technique includes etching, for example isotropicdry and/or wet etching. Etching may be conducted selectively (ideally,highly selectively) relative to lines 36, operative structures 31, anddummy structures 32. FIG. 10 is a view of the FIG. 9 substrate whereindielectric material 14 added in FIG. 2 is removed solely for clarity insuch drawing.

The above processing discloses but example embodiments of formingcircuitry components in accordance with some aspects of the invention.In one embodiment, a method of forming circuitry components comprisesforming a stack of horizontally extending and vertically overlappingfeatures. By way of example only, such features may comprise plates,with the example depicted structure of plates 14 comprising but oneexample of such plates. Regardless, in such embodiment, the stackcomprises a primary portion and an end portion wherein at least some ofthe features increase in horizontal extent in the vertical inwarddirection in the end portion of the stack (i.e., at least some of whichextend farther in the horizontal direction in the end portion movingdeeper into the stack in the end portion). Operative structures 31(e.g., circuit components) are formed vertically through the features inthe primary portion and dummy structures 32 (e.g., dummy circuitcomponents) are formed vertically through the features in the endportion. The processing depicted through FIG. 4, or through FIGS. 5-8,are examples. The operative and dummy structures may comprise the samematerial, and in one embodiment may consist essentially of the samematerial. The dummy structures may support material of the features fromvertical movement in the end portion while at least some of sacrificialmaterial that is elevationally between the material of the features inthe primary and end portions is removed. The processing depicted ingoing from that of FIGS. 5-8 to that of FIGS. 9 and 10 is but one suchexample processing. With respect to a prior art problem, dummystructures heretofore have not been provided in a stair-like end portionof an array. Accordingly, the floors/ceilings that are verticallybetween the respective void spaces 29 in FIGS. 9 and 10 may be sagged,bent, or broken during processing due to lack of support. In accordancewith one embodiment of the invention, dummy structures in the endportion support the features (e.g., the respective ceilings and floors,or plates) from vertical movement, for example by laterally engagingside portions of such floors/ceilings that were created where such dummystructures extend there-through. Regardless, other attributes asdescribed may be employed.

Additional processing may occur in fabricating integrated circuitry, forexample in fabricating an array of memory cells as next described withreference to FIGS. 11-13. Referring to FIGS. 11 and 11A, material 40 hasbeen isotropically deposited within horizontally elongated openings 34,former void spaces 29 (not shown in FIGS. 11, 11A), and any remainingvolume of openings 25, 27. Material 40 has subsequently been removedfrom horizontally elongated openings 34 to form vertically spacedhorizontal conductive lines 42 within the void spaces elevationallybetween horizontal lines 36 of dielectric material 14. In oneembodiment, conductive lines 42 collectively cross a row of theoperative and dummy structures at different respective elevations. Inone embodiment, individual structures 31, 32 cross different conductivelines at different respective elevations. In the depicted example,conductive lines 42 extend longitudinally straight linear. Alternatelyby way of example, some or all of lines 42 may not be straight linear,for example being longitudinally curvilinear (not shown). Material 40may also be removed from the remaining internal volume of openings 25,27 as shown. FIG. 12 depicts the circuitry of FIG. 11 wherein thedielectric material that is shown as being deposited in FIG. 2 isremoved solely for clarity.

FIGS. 11, 11A, and 12 depict but one example embodiment comprising NANDcircuitry wherein operative structures 31 comprise interconnectedchannel regions of a NAND string. In such example embodiment, material40 comprises a composite of a suitable tunnel dielectric 49 (FIG. 11A),floating gate/charge trapping material 48, dielectric 50, and conductivecontrol gate material 52. Thereby, conductive material 52 provides butan example conductive portion of conductive lines 42 that is within thevoid spaces between the horizontal lines of dielectric material, andwhich collectively cross a row of the operative and dummy structures atdifferent respective elevations. Individual ones of the memory cells ofthe example circuitry of FIGS. 11 and 11A comprise an intersection of anindividual horizontal conductive line and an individual operativestructure (e.g., in the form of a string of channels of NAND), and someof which are indicated with reference numeral 55.

In one embodiment, a respective contact may be formed to a stairextension of individual ones of horizontal conductive lines 42 in endportion 20 for making communicative connection to circuitry. One suchexample is diagrammatically shown in FIG. 13. The dielectric material 14of FIG. 2 is again showed removed solely for clarity in depictingcertain components. Specifically, FIG. 13 shows example individualcontacts 60 (e.g., current conductive contacts) which may be formedthrough the dielectric material 14 (not shown) of FIG. 2 for makingcommunicative connection to circuitry, such as that elevationallyoutward of that depicted by FIG. 13 with respect to each conductive line42.

Circuitry components other than or in addition to components of memorycells may be fabricated in accordance with embodiments of the invention.

An example embodiment of a method of forming an array of cross-pointmemory cells is next described with reference to FIGS. 14-17. Likenumerals from the above-described embodiments have been used whereappropriate, with some construction differences being indicated with thesuffix “a” or with different numerals. FIG. 14 depicts an alternateembodiment substrate fragment 10 a to that depicted by FIG. 4. In FIG.14, openings 25, 27 have been lined with a first material 62. In oneembodiment, such material is dielectric (i.e., a 15 to 30 Angstromsthick layer of undoped silicon dioxide). Thereafter, a programmablematerial 30 was deposited to line over first material 62 within openings25, 27. Then, remaining volume of openings 25, 27 has been filled withconductive material 64, and materials 62, 30, and 64 planarized back tomaterials 14 and 16. Horizontally elongated openings (not shown in FIG.14) may then be formed analogous to the processing depicted by FIGS.5-8.

Programmable material 30 may be solid, gel, amorphous, crystalline, orany other suitable phase. Any existing or yet-to-be developedprogrammable material may be used, with only some examples beingprovided below.

One example programmable material is ion conductive material. Examplesuitable such materials comprise chalcogenide-type (for instance,materials comprising one or more of germanium, selenium, antimony,tellurium, sulfur, copper, etc.; with example chalcogenide-typematerials being Ge₂Sb₂Te₅, GeS₂, GeSe₂, CuS₂, and CuTe) and/or oxidessuch as zirconium oxide, hafnium oxide, tungsten oxide, copper oxide,niobium oxide, iron oxide, silicon oxide (specifically, silicondioxide), gadolinium oxide, etc. capable of inherently (or withadditive) supporting electrolyte behavior. Such may have silver, copper,cobalt, and/or nickel ions, and/or other suitable ions, diffused thereinfor ionic conduction, analogously to structures disclosed in U.S. Pat.No. 7,405,967 and U.S. Patent Publication Number 2010/0193758.

Additional example programmable materials include multi-resistive statemetal oxide-comprising material. Such may comprise, for example, atleast two different layers or regions generally regarded as orunderstood to be active or passive regions, although not necessarily.Alternately, such may only comprise active material. Example active cellregion compositions which comprise metal oxide and can be configured inmulti-resistive states include one or a combination ofSr_(x)Ru_(y)O_(z), Ru_(x)O_(y), and In_(x)Sn_(y)O_(z). Other examplesinclude MgO, Ta₂O₅, SrTiO₃, SrZrO₃, BaTiO₃, Ba_((1-x))Sr_(x)TiO₃,ZrO_(x) (perhaps doped with La), and CaMnO₃ (doped with one or more ofPr, La, Sr, or Sm). Example passive cell region compositions include oneor a combination of Al₂O₃, TiO₂, and HfO₂. Regardless, a programmablematerial composite might comprise additional metal oxide or othermaterials not comprising metal oxide. Example materials andconstructions for a multi-resistive state region comprising one or morelayers including a programmable metal oxide-comprising material aredescribed and disclosed in U.S. Pat. Nos. 6,753,561; 7,149,108;7,067,862; and 7,187,201, as well as in U.S. Patent ApplicationPublication Nos. 2006/0171200 and 2007/0173019. Further as isconventional, multi-resistive state metal oxide-comprising materialsencompass filament-type metal oxides, ferroelectric metal oxides andothers, and whether existing or yet-to-be developed, as long asresistance of the metal oxide-comprising material can be selectivelychanged.

The programmable material may comprise memristive material. As anexample, such material may be statically programmable semiconductivematerial which comprises mobile dopants that are received within adielectric such that the material is statically programmable between atleast two different resistance states. At least one of the statesincludes localization or gathering of the mobile dopants such that adielectric region is formed and thereby provides a higher resistancestate. Further, more than two programmable resistance states may beused. In the context of this document, a “mobile dopant” is a component(other than a free electron) of the semiconductive material that ismovable to different locations within said dielectric during normaldevice operation of repeatedly programming the device between at leasttwo different static states by application of voltage differential tothe pair of electrodes. Examples include atom vacancies in an otherwisestoichiometric material, and atom interstitials. Specific example mobiledopants include oxygen atom vacancies in amorphous or crystalline oxidesor other oxygen-containing material, nitrogen atom vacancies inamorphous or crystalline nitrides or other nitrogen-containing material,fluorine atom vacancies in amorphous or crystalline fluorides or otherfluorine-containing material, and interstitial metal atoms in amorphousor crystalline oxides. More than one type of mobile dopant may be used.Example dielectrics in which the mobile dopants are received includesuitable oxides, nitrides, and/or fluorides that are capable oflocalized electrical conductivity based upon sufficiently high quantityand concentration of the mobile dopants. The dielectric within which themobile dopants are received may or may not be homogenous independent ofconsideration of the mobile dopants. Specific example dielectricsinclude TiO₂, AlN, and/or MgF₂. Example programmable materials thatcomprise oxygen vacancies as mobile dopants may comprise a combinationof TiO₂ and TiO_(2-x) in at least one programmed resistance statedepending on location of the oxygen vacancies and the quantity of theoxygen vacancies in the locations where such are received. An exampleprogrammable material that comprises nitrogen vacancies as mobiledopants is a combination of AlN and AlN_(1-x) in at least one programmedstate depending on location of the nitrogen vacancies and the quantityof the nitrogen vacancies in the locations where such are received. Anexample programmable material that comprises fluorine vacancies asmobile dopants may is a combination of MgF₂ and MgF_(2-x) in at leastone programmed resistance state depending on location of the fluorinevacancies and the quantity of the fluorine vacancies in the locationswhere such are received. As another example, the mobile dopants maycomprise aluminum atom interstitials in a nitrogen-containing material.

Still other example programmable materials include polymer materialssuch as Bengala Rose, AlQ₃Ag, Cu-TCNQ, DDQ, TAPA, and fluorescene-basedpolymers.

Referring to FIG. 15, such corresponds in processing sequence to that ofFIG. 9 of the above-described embodiments. Sacrificial material 12 (notshown) has been at least partially removed (e.g., by etching) betweendielectric lines 36 in primary portion 18 and end portion 20 laterallybetween horizontally elongated openings 34. Material 12 may be etchedselectively (ideally, highly selectively) relative to dielectric lines36, first material lining 62, and conductive material 64 in openings 25,27. FIGS. 14 and 15 depict an example embodiment wherein the operativeand dummy structures comprise a plurality of the same materials, and insuch embodiment arranged in the same lateral order relative one anotherin the operative and dummy structures. Regardless, in one embodiment,first material lining 62 may serve as a protecting barrier from adverseexposure of programmable material 30 to the etching chemistry whichetches the sacrificial material.

Referring to FIG. 16, at least a portion of first material 62 has beenremoved elevationally between dielectric lines 36 to expose laterallyouter sidewalls of programmable material 30 that is elevationallybetween dielectric lines 36. An example technique for doing so wherematerial 62 comprises silicon dioxide includes etching with a dilute HFsolution.

Referring to FIG. 17, at least a portion of sacrificial material 12 (notshown) of FIG. 14 has been replaced with conductor material 52 (e.g.,current conductive material) that is in electrical connection with thelaterally outer sidewalls of programmable material 30 and to comprisevertically spaced horizontal conductive lines 42 a. Materials 64 and 52may be of the same composition or of different compositions. Further andregardless, conductive material 64 within remaining volumes of openings25, 27 alternately may be provided subsequent to the etching depicted byFIG. 15. Regardless, FIG. 17 also depicts conductor material 52 ashaving been at least partially removed from horizontally elongatedopenings 34 to form such vertically spaced horizontal conductive lines42 a.

Individual ones of the cross-point memory cells comprise crossing onesof the horizontal conductive lines in the primary portion and conductivematerial in the openings in the primary portion having the programmablematerial there-between, with some of such example memory cells beingindicated with reference numeral 55 in the FIG. 17 example embodiment.

An embodiment of the invention includes a stack of horizontallyextending and vertically overlapping features. The stack comprises aprimary portion and an end portion. At least some of the features extendfarther in the horizontal direction in the end portion moving deeperinto the stack in the end portion. Operative structures extendvertically through the features in the primary portion. Dummy structuresextend vertically through the features in the end portion. In oneembodiment, the features may be horizontally extending lines, forexample formed of any one or combination of conductive (e.g., currentconductive), semiconductive, and/or dielectric material(s). In oneembodiment, the features comprise a combination of horizontallyextending conductive and dielectric lines (e.g., overlapping andalternating such lines). In one embodiment, contacts may be in the endportion, for example extending vertically to the lines. Any otherattribute as described above may be used, for example as shown anddescribed with respect to FIGS. 1-13 and with respect to FIGS. 14-17.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

The invention claimed is:
 1. A method of forming an array of cross-pointmemory cells, comprising: forming a stack of horizontally extending andvertically overlapping dielectric features, the stack comprising aprimary portion and an end portion, at least some of the dielectricfeatures extending farther in the horizontal direction in the endportion moving deeper into the stack in the end portion; formingopenings through the dielectric features in the primary portion and inthe end portion; lining the openings with first material; lining thefirst material-lined openings with programmable material; fillingremaining volume of the first and programmable material-lined openingswith conductive material; forming horizontally elongated trenchesthrough the dielectric features to form horizontally elongated andvertically overlapping dielectric lines from dielectric material of thedielectric features, the dielectric lines individually extending fromthe primary portion into the end portion and individually laterallyabout sides of both the openings in the primary and end portions;removing at least some of sacrificial material that is elevationallybetween the dielectric lines in the primary and end portions laterallybetween the trenches selectively relative to the dielectric lines andthe first material lining in the openings; after removing at least aportion of the sacrificial material, removing at least a portion of thefirst material that is elevationally between the dielectric lines toexpose laterally outer sidewalls of the programmable material that iselevationally between the dielectric lines; and replacing at least aportion of the sacrificial material with conductor material that is inelectrical connection with the laterally outers sidewalls of theprogrammable material and to comprise vertically spaced horizontalconductive lines; individual ones of the cross-point memory cellscomprising crossing ones of the horizontal conductive lines in theprimary portion and conductive material in the openings in the primaryportion having the programmable material there-between.
 2. The method ofclaim 1 comprising forming the trenches after the filling.
 3. The methodof claim 1 wherein the conductive material and the conductor materialare of the same composition.
 4. The method of claim 1 wherein theconductive material and the conductor material are of differentcompositions.
 5. The method of claim 1 wherein the first material isdielectric.
 6. The method of claim 1 wherein the features compriseplates.
 7. The method of claim 1 comprising forming the primary portionopenings and the end portion openings at the same time.
 8. The method ofclaim 1 comprising forming the primary portion openings and the endportion openings at different times.
 9. The method of claim 1 comprisingforming at least some of the end portion openings to horizontallyoverlap ends of individual ones of the features.
 10. The method of claim1 comprising forming the primary portion openings and the end portionopenings to have the same horizontal and vertical cross sections. 11.The method of claim 1 comprising forming the primary portion openingsand the end portion openings to have at least one of differenthorizontal cross sections or different vertical cross sections.
 12. Amethod of forming circuitry components, comprising: forming a stack ofhorizontally extending and vertically overlapping features, the stackcomprising a primary portion and an end portion, at least some of thefeatures extending farther in the horizontal direction in the endportion moving deeper into the stack in the end portion; forming firststructures vertically through the features in the primary portion andforming second structures vertically through the features in the endportion; removing at least some sacrificial material that iselevationally between material of the features in the primary and endportions to form void spaces elevationally between the horizontallyextending and vertically overlapping features; and forming conductormaterial within the void space and forming a stack of horizontallyextending and vertically overlapping conductive lines from the conductormaterial.
 13. The method of claim 12 comprising forming the conductivematerial of the conductive lines to horizontally wrap around the firststructures.
 14. The method of claim 12 comprising forming the firststructures to at least initially comprise hollow cylinders.
 15. Themethod of claim 14 comprising forming conductive material to extendvertically within the hollow cylinders.
 16. The method of claim 15wherein the conductive material is formed after forming the conductormaterial.
 17. The method of claim 15 wherein the conductive material isformed before forming the conductor material.
 18. A method of forming anarray of cross-point memory cells, comprising: forming a stack ofhorizontally extending and vertically overlapping dielectric features,the stack comprising a primary portion and an end portion, at least someof the dielectric features extending farther in the horizontal directionin the end portion moving deeper into the stack in the end portion;forming openings through the dielectric features in the primary portionand in the end portion; lining the openings with first material; formingprogrammable material and conductive material within the firstmaterial-lined openings; forming horizontally elongated trenches throughthe dielectric features to form horizontally elongated and verticallyoverlapping dielectric lines from dielectric material of the dielectricfeatures, the dielectric lines individually extending from the primaryportion into the end portion and individually laterally about sides ofboth the openings in the primary and end portions; removing at leastsome of sacrificial material that is elevationally between thedielectric lines in the primary and end portions laterally between thetrenches selectively relative to the dielectric lines and the firstmaterial lining in the openings; after removing at least a portion ofthe sacrificial material, removing at least a portion of the firstmaterial that is elevationally between the dielectric lines to exposelaterally outer sidewalls of the programmable material that iselevationally between the dielectric lines; and replacing at least aportion of the sacrificial material with conductor material that is inelectrical connection with the laterally outers sidewalls of theprogrammable material and to comprise vertically spaced horizontalconductive lines; individual ones of the cross-point memory cellscomprising crossing ones of the horizontal conductive lines in theprimary portion and conductive material in the openings in the primaryportion having the programmable material there-between.
 19. The methodof claim 12 comprising forming the conductive lines to compriseconductive lines of cross-point memory cells.